In a gas turbine engine, air is pressurized in a compressor and mixed with fuel in a combustor for generating hot combustion gases that flow downstream through turbine stages where energy is extracted. Large industrial power generation gas turbine engines typically include a can combustor having a row of individual combustor cans in which combustion gases are separately generated and collectively discharged. Since the can combustors are independent and discrete components, each generating its respective combustion heat stream, the static and dynamic operation of the cans are inter-related.
Of particular concern to effective operation of can combustor engines is combustion dynamics, i.e., dynamic instabilities in operation. High dynamics are often caused by fluctuations in such conditions as the temperature of the exhaust gases (i.e., heat release) and oscillating pressure levels within a combustor can. Such high dynamics can limit hardware life and/or system operability of an engine, causing such problems as mechanical and thermal fatigue. Combustor hardware damage can come about in the form of mechanical problems relating to fuel nozzles, liners, transient pieces, transient piece sides, radial seals, impingement sleeves, and others. These problems can lead to damage, inefficiencies, or blow outs due to combustion hardware damage.
Thus, there have been various attempts to control combustion dynamics, thus preventing degradation of system performance. There are two basic methods for controlling combustion dynamics in an industrial gas turbine combustion system: passive control and active control. As the name suggests, passive control refers to a system that incorporates certain design features and characteristics to reduce dynamic pressure oscillations or heat release levels. Active control, on the other hand, incorporates a sensor to detect, e.g., pressure or temperature fluctuations and to provide a feedback signal which, when suitably processed by a controller, provides an input signal to a control device. The control device in turn operates to reduce dynamic pressure oscillations or excess heat release levels.
In considering the dynamic effects of both pressure fluctuations and heat release, it has been recognized in accordance with aspects of the present subject matter that there is a constructive coupling between the pressure oscillations and the heat release oscillations. In particular, combustion dynamics are increased when the heat release and pressure fluctuations are in phase with one another. Known solutions for mitigating passive dynamics have thus sought to reduce dynamics by one or more techniques, such as decoupling the pressure and heat release oscillations (e.g., by changing the flame shape, location, etc. to control heat release within a combustion engine) or dephasing the pressure and heat release.
One known apparatus used to address some dynamics concerns in various applications is a resonator. Although resonator assemblies have been used, their application has apparently been limited to the attenuation of high frequency instabilities by pure absorption of acoustic energy. For example, quarter wave resonators have been used to suppress acoustic energy in a combustion turbine power plant or to change the acoustic nature of a combustor in aviation applications.
The art is continuously seeking improved systems and methods for reducing high combustion dynamics, to improve system efficiency and extend the useful life of gas turbine engine components.